1 Field of the Invention
The present invention relates to a rear projector which displays an image on a screen panel by projected projection light from behind the screen panel.
2 Description of the Related Art
With proliferation of digital broadcasting and widespread use of digital AV (audio-visual) devices in recent years, there is an increasing demand for displays capable of displaying images of high quality on a large screen. As a display of this kind, the present assignee has already proposed a rear projector which displays images by the rear projection method, in Japanese Laid-Open Patent Publication (Kokai) No. 2002-296678. In the rear projector, part of which is shown in FIG. 4, a projection device disposed within a housing 13 modulates incident light (white light) from a light source lamp into projection light for image display, based on image information inputted from an external image information output device, and projects the projection light onto a screen panel 20 disposed at the front of the housing 13, from behind, to thereby display images on the screen panel. In this case, the projection device is provided with modulation means for modulating the incident light and a cooling fan for cooling the light source lamp and the modulation means.
In general, the screen panel of a rear projector of the above mentioned kind thermally expands vertically and laterally according to a rise in temperature thereof caused by projected of projection light. For this reason, if the screen panel is configured such that its periphery is fixed to the housing, expansion of the screen panel is inhibited, which can cause warpage of the screen panel. To overcome this problem, in the proposed rear projector, the screen panel 20 is attached to the housing 13, as shown in FIG. 4, such that the screen panel 20 is held by the housing 13 in an expandable fashion without having its periphery fixed to the housing 13. In this case, a protective tape for preventing scratching is affixed to the periphery of the screen panel (or to the edge portion of an opening of the housing for receiving the screen panel) so as to prevent the screen panel from being scratched by sliding contact between the periphery of the screen panel and the edge portion of the opening of the housing when the screen panel expands. Thus, distortion of the screen panel due to its expansion and scratched on the periphery of the screen panel are prevented.
However, from the study of the proposed rear projector, the present inventors found out the following point for improvement: In this rear projector, because the composition in which the screen panel is maintained while possible to be extended is adopted, a gap is formed between the periphery of the screen panel 20 and the edge portion of the opening of the housing 13 as illustrated in FIG. 4. Further, in the rear projector, since the modulation means and the light source lamp are cooled by air blown from the cooling fan, there is a flow of air within the housing. As a result, dust can enter the housing together with air through the gap formed between the screen panel and the housing. Therefore, in the rear projector, the dust having entered the housing through the gap can be deposited on the projection device and the rear surface of the screen panel. This is the point desired to be improved in the proposed rear projector.